[TowerTalk] Wireman W2DU Current Type Balun

[Lux, Jim]

On 12/25/22 2:05 AM, Jim Brown wrote:
> Hi Paul,
>
> I made S21 measurements using a test jig quite similar to Steve's. His 
> measurement technique seemed quite good. The (major) shortcoming of 
> his work is that he measured only chokes on only a few cores, failing 
> to understand the contribution of production tolerances to 
> reproducible designs.

What are the dominant sources of variation?  Material or "assembly"

The material datasheet claims 20% uncertainty in the properties 
(although I don't know if that is "run to run" or "piece to piece within 
a run") - They're sintered from a powder, and having just looked a a 
bunch of micrographs of gas line filters made using a similar process, i 
was surprised how much variation there is in that process, within a batch.

I would think there is substantial variation due to how the turns are 
wound on the core (how tight, spacing, etc.) Particularly in terms of 
parasitic C between turns.




>
> A limitation on the precision of my data is that my fixture had to 
> allow measurement of many hundreds of chokes on many cores, not a few.
>
> 73, Jim K9YC
>
>  On 12/25/2022 12:02 AM, Paul Christensen wrote:
>> Jim (K9YC),
>>
>> When making Rs measurements are you using the S11 or S21 method?  Steve,
>> G3TXQ was an advocate of S21 while Owen, VK2OMD claims S11 results in 
>> better
>> accuracy with high Rs values.
>>
>> I've been using S21 with G3TXQ's VNA adapter on a PC board. It's 
>> shown at
>> the bottom of the page in the link below:
>>
>> http://www.karinya.net/g3txq/chokes/
>
>
>
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